Electrode array for use in electrochemical cells

ABSTRACT

The invention features an electrode array ( 7 ) in which pairs of electrodes ( 1 ) are geometrically arranged so that the broadest faces of the exposed electrodes are not directly opposing to each other. Rather, the broadest facing surfaces of the electrodes in the array are parallel, adjacent, or offset at an angle. The electrode geometry of an electrode array of the invention permits electrodes to be in close proximity, thereby lowering series resistance, while minimizing the possibility for short circuits that can cause electrical leakage. An electrode array of the invention can be used in an electrochemical cell, such as a battery, e.g., a lithium battery, a capacitor, a flow-through capacitor, or a fuel cell.

REFERENCE TO PRIOR APPLICATION

This application is based on and claims priority from U.S. ProvisionalPatent Application Ser. No. 60/307,789, filed Jul. 25, 2001, herebyincorporated by reference in its entirety.

GOVERNMENT CONTRACT

This invention was funded under contract with the Army Research Office,under Contract No. DDAD 19-00-C-0448. The United States Government mayhave certain rights in the invention.

FIELD OF THE INVENTION

The field of the invention is electrodes for electrochemical cells.

BACKGROUND OF THE INVENTION

In electrochemical cells, such as capacitors, batteries, fuel cells, andflow-through capacitors, it is desirable to reduce series resistance andelectrical leakage, which waste energy. Normally, to reduce seriesresistance, it would be desirable place the electrodes close together.However, proximity is difficult to achieve with purely opposingelectrodes. In order to place the electrodes close together, forexample, closer than 0.03 inches (˜760 μm), the dielectric between themmust be thin, but this geometry has the undesirable effect of increasingthe electrical leakage. Moreover, where the electrochemical cell is aflow-through capacitor, thin dielectric spacers lead to a drop inpressure. Therefore, it is desirable to provide for a new and improvedelectrochemical cell with minimal series resistance and with lowelectrical leakage.

SUMMARY OF THE INVENTION

The invention features an electrode array in which pairs of electrodesare geometrically arranged so that the broadest exposed faces of theelectrodes are not directly opposed to each other. Rather, the broadestfaces of the electrodes in the array are parallel, adjacent, or offsetat an angle. The electrode geometry of an electrode array of theinvention permits electrodes to be in close proximity, thereby loweringseries resistance, while minimizing the possibility for short circuitsthat, can cause electrical leakage.

The electrode array of the present invention may function as an anode,cathode, or as a stand-alone capacitor or electrochemical cell combiningcathodes and anodes in one sheet of material.

Electrodes may be formed as patterns of lines, dots, or other shapesplaced on, attached, or formed onto a substrate, including a conductivematerial, or, alternatively, a nonconductive sheet material. Theselines, dots, etc., may be formed in very thin layers and may be spacedvery close. An electrochemical cell, fuel cell, battery, capacitor, orflow-through capacitor is formed by the adjacent pairs or groups oflines and dots.

Thus, one aspect the invention features an array of electrodes, wherebythe broadest exposed electrode faces of the electrodes are adjacent toeach other. Alternatively, the broadest faces of the exposed electrodesare coplanar or offset at an angle, but not directly opposite to eachother, whether on the same sheet of a material containing both anodesand cathodes, or between separated anode sheets and cathode sheets. Thisminimizes the possibility for short circuits that cause leakage. Theelectric field comes up out of the anodes and curves back to thecathode. The electrodes of the array can be dots, shapes, or lines thatcan be recessed into the dielectric spacer as a further means ofprotecting against electrical leakage between them.

The electrode array of the present invention uses a geometricarrangement of parallel, adjacent, or offset electrodes in order tocreate capacitors, electrochemical cells, or flow-through capacitors. Adielectric insulator serves as a spacer between adjacent electrodes; thespacer may be a porous, nonporous, ion-permeable, ion-selective,membrane, or other dielectric material. Optionally, current collectorsare in electrical contact with the electrodes, either placed under, orembedded in, or sandwiched between, the electrodes.

The adjacent geometry of the electrodes within the electrode arrayreduces series resistance and leakage sufficiently that the distancebetween the anode and the cathode can be less than 0.03 inches, or canpreferably be reduced to 0.005 inches, or to less than 0.001 inches.Electrode materials in any shapes separated by insulating materials maybe manufactured with a narrow distance between adjacent electrodes,reduced to 1 micron or less, by using manufacturing methods commonlyused to print circuit boards in the semiconductor industry. Where it ispreferred to use a wider space between the electrodes, for example, over0.001 cm, manufacturing methods such as screen or other printing orcoating methods will suffice to manufacture the electrode array of thepresent invention.

The electrode array of the invention can be used in any type ofelectrochemical cell, such as capacitors, batteries, and fuel cells. Anelectrode array of the invention can be a used in a flow-throughcapacitor. Alternatively, an electrode array of the invention can beused in a lithium battery.

In one embodiment, the electrode array is comprised of dots, shapes, orlines that may be recessed into the spacer as a further means ofprotecting against electrical leakage between them. The broadest facesof the electrodes are offset from each other.

An additional advantage of the present invention is that the electrodearrays may be lines, dots, or any other shapes that can be arranged inpatterns with small distances between shapes of each pair of electrodes,for example, less than 3 millimeters, thereby allowing construction ofan electrode array containing anode-cathode pairs within a single sheetof material. Therefore, the electrode array sheet may compriseanode-cathode pairs to act as an integrated capacitor, electrochemicalcell, or flow-through capacitor. These electrode array sheets,containing one or more anode-cathode pairs per sheet, may be stackedtogether in any geometry known to prior art flow-through capacitors,electrochemical cells, water filters, batteries, or electroniccapacitors.

In one embodiment, the electrode pattern of the present invention formsa two-dimensional electrode array. The electrode array may be used as adouble-layer capacitor, capacitor, flow-through capacitor, fuel cell, orany other electrochemical device. The thin electrodes, for example, lessthan 0.13 cm thick, and thin spacing, for example, less than 0.13 cmapart, of this array reduce leakage and ESR. Leakage is reduced becausethe broadest face of each electrode of an electrode pair is offset fromthe other electrode. Because the electrodes may be placed close togetherwithout generating electrical leakage, series resistance is reduced.Series resistance of less than 50 ohms/cm² of electrode array facialarea and leakage resistance of more than 30 ohms/cm² of electrode arrayfacial area can be achieved by the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a frontal illustration of an embodiment of an electrode arraythat includes two parallel electrodes and a spacer, optionally separatedby a current collector.

FIG. 1B is a cross-sectional view of the electrode array shown in FIG.1A.

FIG. 2 is an illustration of an electrode array in which adjacentconcentric electrodes are separated by a dielectric spacer.

FIG. 3 shows two of the concentric electrode arrays illustrated in FIG.2, separated by a flow spacer, which forms a flow path.

FIG. 4 shows a layered geometry for designing and manufacturing anelectrode array according to the present invention, where (A) is a basesupporting layer; (B) is a an insulating layer formed by forming apattern of dielectric spacer on the base substrate shown in (A); (C)shows a linear array of electrode material placed on top of the portionsof the substrate that remain exposed in layer (B); (D) shows an optionaladditional set of electrodes which are electrically insulated from theelectrodes deposited in (C); and (E) is a second current collectoroptionally placed against the electrode array shown in (D).

FIG. 5 shows an electrode array in which the electrodes may optionallyeither protrude from or be embedded in a substrate. The substrate mayoptionally be an insulating layer or current collector. The electrodesare coplanar and may have either underlying or overlying currentcollectors.

FIG. 6 shows an electrode array in which the electrodes are coplanar andadjacent to each other within the same sheet of material.

FIG. 7 illustrates two electrode arrays placed together.

FIG. 8 illustrates a flow channel formed by the misalignment of groovesbetween two electrode arrays.

FIG. 9 illustrates an alternative design of a flow-through capacitor orflow-through electrochemical cell utilizing an electrode array in aspiral-wound configuration.

DETAILED DESCRIPTION

The electrode array of the present invention may be used in double-layercapacitors; flow-through capacitors or electrochemical cells; solidpolymer electrolyte or nonelectrolyte-containing capacitors;nonelectrolytic, nonelectrolyte-containing, solidelectrolyte-containing, or in nondouble layer batteries or capacitors,by use of any conductive metal or material for the electrode, and use ofany dielectric material for the spacer, including ceramic, polymer,MYLAR® (MYLAR is a registered trademark of E.I. Du Pont De Nemours andCompany Corporation of Wilmington, Del.) sheet material, or any othermaterials commonly used to make film-type capacitors. Arrays ofelectrodes of the present invention may also be used for lithium storageor other intercalation battery devices, either combined with anelectrolyte or with a solid polymer electrolyte material.

A preferred embodiment of the present invention is the use of the arrayfor electrolyte-containing electrochemical cells and flow-throughcapacitors. Any carbon or carbon binder mixture known in the art indoublelayer capacitors may be used. Gel and hydrogel binders are alsoefficacious, including use of ion-permselective (i.e., selectivepermeability) or cross-linked, ion exchange, polyelectrolyte gels. Whereboth anodes and cathodes are included in the same sheet array material,the sheet itself may form an entire electrochemical cell or flow-throughcapacitor. These sheets may be stacked together in any geometry known toflow-through capacitors, batteries, or water filters, including spiralwound, pleated, stacked polygon, or disc. Where anode-cathode pairs arecontained within the same sheet of material, each sheet itself functionsas an electrochemical cell. In this way, anode and cathode pairs do notneed to be formed between two opposing layers or sheets. The spacingbetween adjacent anode-cathode electrode pairs within the same sheet maybe small, and no longer simultaneously depends upon the thickness of theflow spacer, as in prior art flow-through capacitors, electrochemicalcells, and flow-through electrochemical cells. The spacer does not needto do double duty as both an insulator, which requires thinness for lowseries resistance, and a flow channel, which has the oppositerequirements of open area. Therefore, when used in flow cells, such asflow-through capacitors and fuel cells, the spacing between opposingelectrode array sheets may be much thicker than the spacing betweensheet electrodes of prior art electrochemical cells. Because the sheetelectrodes of the present invention can constitute complete electriccells, unlike prior art electrochemical cells, the separation distancebetween sheet electrodes may be increased without substantiallyincreasing series resistance. For example, the surfaces of the sheetelectrode or electrode array may be separated by flow spacers or spacersof greater than 0.002 cm thick, for example, up to 1.0 cm thick or more.No flow spacer at all may be used, in which case the electrolyte,working fluid, or purification or concentration feed stream may besimply flowed past or over the electrode array. Where flow spacers areused, the cells may be made using any cartridge geometry, cartridgeholders common to prior art flow-through capacitors, or electrochemicalcells, with the option that spacers between layers may be replaced byholding the layers apart under tension, with shims or supports placedmore than 1.0 mm apart, or alternatively, the thicker spacers above maybe used to achieve low pressure drops of less than 2 kilograms persquare centimeter and not significantly increase series resistance.

U.S. Pat. No. 6,110,354, issued Aug. 29, 2000, teaches electrode arraysused for electrochemical sensors, whereby the nonfaradaic, capacitancecomponent is minimized. An additional purpose of the present inventionis to maximize the nonfaradaic, capacitance component used in energygeneration, energy storage, or other electrochemical cells. This is doneby the selection of relatively high surface area electrode materials.For use in capacitors and many other electrochemical cells, a preferredembodiment of the present invention is use of electrode material with asurface area of over 10 square meters per grain B.E.T. For use incapacitors, certain batteries, and other electrochemical cells,electrode materials with a surface area of over 300 m2 per gram arepreferred. Otherwise, U.S. Pat. No. 6,110,354 and the references citedtherein teach methods of manufacture and electrode array geometries thatmay be directly adapted to the present invention by the incorporation ofsaid relatively high surface area electrode materials. The presentinvention may make use of electrodes with the less than 100 micronspacing described in U.S. Pat. No. 6,110,354, or, may alternatively makeuse of wider electrodes with over 10 to 1000 times greater surface areaand spacing than described in U.S. Pat. No. 6,110,354. All the means offabricating and interconnecting electrodes, as well as the generalgeometry and method of making flow channels with or of the electrodesdescribed in U.S. Pat. No. 6,110,354 may be used in the presentinvention. Use of inert electrode materials, such as graphite, gold,platinum series metals, and any form of carbon, is particularlypreferred. However, for use in many batteries, electrochemicallyreactive metals, and other conductive compounds which form reversiblesurface area compounds or complexes may be preferentially used.

Another preferred form of the present invention is the selection ofelectrode array dimensions, whereby the distance between anode andcathode electrodes is less than the diffusion length of the electrolytesolute for a given charge cycle time.

The electrode array of the present invention may also be used foranalytical electrochemistry of any material present in the electrolyte,including organic, inorganic, or biological compounds.

FIG. 1A shows a frontal view of the broadest faces of electrodes 1 in anelectrode array 7 formed from two electrodes 1 that are in the shape oflines and are arranged in parallel. The electrodes 1 are separated byspacer 2, and optionally separated by a current collector 6. Optionalparallel lead means 5 connect alternating electrodes 1 into alternatingarrays of anodes and cathodes. Lead means 5 may also be used to connectevery two or more alternate electrodes 1. Alternatively, lead means 5may be used to connect only the end electrodes 1, in order to formelectrodes in series.

FIG. 1B is a cross-sectional view showing the thin edge of one electrode1 line and its underlying optional current collector 6. The broadestface of electrode 1 is perpendicular to the page. This current collector6 may typically be metal or graphite, and the electrode 1 may typicallybe a high capacitance carbon held together with a binder, for use indoublelayer capacitors, flow-through capacitors, or electrochemicalcells, or, may be aluminum or other metal for use ira solid polymerelectrolyte or nonelectrolyte-containing capacitors.

The electrode array 7 of FIG. 1 is formed by any manufacturing methodable to form patterns of adjacent lines or shapes, such as by coating,printing, extruding, coextruding, spraying, or electroplating theelectrodes 1 onto a spacer 2. Coating methods may include, but are notlimited to: dip, brush, knife, roll, airbrush, spray, extruded, print,cast, and strip coating.

FIG. 2 shows an electrode array 7 formed by adjacent concentric spiralor circle electrodes 1 sandwiching spacer or spacers 2. The broadestface of each electrode is directed outward from the page. Thiscombination, with optional current collectors 6 that may underlie oroverlay the electrode layers, forms the electrode array 7 of the presentinvention. Current collectors 6 may be placed within or bisect electrodelayers, or form a sandwich with an electrode layer either to the sidesof the current collector 6, perpendicular to the sheet surface, or aboveand below the current collector 6, parallel to the sheet surface.

In FIG. 3, two of the concentric electrode arrays 7 depicted in FIG. 2are arranged for use in a flow-through capacitor or flow-electrochemicalcell. The electrode arrays 7 are separated by a flow spacer 3, whichforms a flow path 4 for the flow of fluid across the electrodes 1. Leads5 can connect to a source of power. Alternatively, leads 5 form a seriesconnection with another capacitor.

FIGS. 4A-4E show a stepwise process of arranging a layered geometry foran electrode array according to the present invention. In FIG. 4A, aplanar sheet is provided to serve as a base or supporting layer on whichto form the electrode array 7. In the embodiment shown, the supportinglayer is prepared from a planar sheet current collector 6, such as asheet of graphite or metal, either alone as a thin sheet, for example,under 0.15 cm thick, a foil sheet, e.g., a foil sheet of less than 0.03cm thick, or a conductive material coated on top of a support material,such as plastic, or MYLAR®, or the like.

In FIG. 4B, an insulating layer is deposited to form a dielectric spacer2. Dielectric spacer 2 can be formed onto the supporting substrate byprocesses known to those skilled in the art. Without limitation, thedielectric spacer 2 can be laced, coated, printed, embossed, engraved,machined, or attached on top of the base layer. This insulating layercan have a geometry of lines, as shown in here, or may be of alternativeshapes, such as dots, squares, stars, polygons, or circles.

In an alternative embodiment, the order of addition of materials used toform these two layers can be reversed. In this configuration (notshown), the substrate layer is formed from a sheet of a dielectricmaterial, on which is deposited a current collector material as thelayer analogous to that shown in FIG. 4B, as lines or other adjacentshapes on top of the supporting substrate.

FIG. 4C shows linear electrode material that has been placed on top ofthe exposed current collector lines of FIG. 4B. One method to do thiswould be to apply or wipe on a capacitance-containing or other electrodematerial, typically a carbon material mixed with a binder. Thiscapacitance material could, for example, fill grooves formed by exposedcurrent collector and flanking spacer layers. Excess can be washed orwiped off. In addition to printing methods of manufacture, variousmethods may be employed to apply this and other layers. For example, anylayer may be etched, deposited from a gas phase, roll coated, spincoated, dip coated, doctor bladed, coated, sprayed, stamped, orelectrocoated, electron beam manufactured, laser and microphotographically plotted, etched, or masked, electrochemically plated orreacted, or otherwise attached or placed upon the exposed currentcollector 6.

FIG. 4D shows an optional additional set of electrodes 1 which areelectrically insulated from the first set of electrodes 1, so that theymay be charged oppositely to these to form either anodes or cathodes.Electrodes 1 may be either anodes or cathodes. In order that theelectrodes 1 may comprise groupings of two or more that may formanode-cathode groups or pairs when placed opposite to each other, thepairs or groups of electrodes 1 must be made on top of insulating layer2. The anodes and cathodes do not have to be equal in number or size.They may optionally be equal in additive surface area if it is desirableas a means to improve function or balance the voltage. It may also bedesirable to connect all electrodes on a given current collector 6together, or to isolate or electrically insulate every other electrode1, or some lesser percentage, for example, 1/100 of 1/10, spaced evenlythroughout the electrode array 7. In this way, half or more of theelectrodes 1 may be connected together to form an anode or cathode, andhalf or less of the remaining electrodes may be connected together toform the oppositely-charged cathode or anode. To form a capacitor, moreor less equal numbers of like electrodes 1, or different numbers ofelectrodes 1 representing equal amounts of capacitive material, shouldbe used.

FIG. 4E is a second current collector 6 that may optionally besandwiched against the electrode array 7 shown in FIG. 4D in order toprovide current to subsets of electrodes 1. Preferably, however, acurrent collector 6 may be printed as lines on top of electrodes 1.These could be cross-connected by a perpendicular lead 5, as shown inFIG. 1.

Generally, the insulating layer is manufactured such that a pattern ofcurrent collector lines, dots, squares, stars, polygons, circles, anyother shapes shows through, is made on top of, or, is produced paralleland adjacent to, the insulating layer(s) 2, creating current collectorlayer(s) 6 with exposed faces. Photo masking, photo lithography, padprinting, screen or other forms of printing are one good ways to makethe structures shown in layers 4B, 4C, and 4D.

FIG. 5 is a cross-sectional schematic view of the electrode array 7shown in FIG. 4D. This shows that the optional current collector 6 mayeither be a continuous layer connecting electrodes 1 together, as shownin the top part of FIG. 1B, or may be arrayed along with the electrodes1 themselves in a discontinuous fashion, restricted on, within, or moreor less congruent with the electrodes 1, as shown in the bottom of FIG.5.

One preferred embodiment of the invention is shown in FIG. 6. Electrodes1 are both coplanar and adjacent within the same sheet of material.Current collectors 6 may underlie, be embedded in, or bisect a doubledelectrode layer, one on each side of the current collector 6.Insulating, dielectric, ionically-conducting or nonionic-conductingspacers 2 prevent electron leakage between electrodes 1, allowing anodeand cathode pairs to form. The anodes and cathodes may be connected inseries or in parallel, for example, as shown in FIG. 1.

FIG. 7 illustrates how two electrode arrays 7 can be placed together inorder to bracket a flow channel. A channel for fluid flow may be formedvia flow spacer 4 by use of an electrically-insulating, added spacermaterial or layer, or a pair of layers, including membranes, nonwoven,and woven materials (not shown) through which a fluid can flow, whichflow spacer 4 may be ionically conductive or not. Any layer mayoptionally be raised, protruded, or recessed above or below the otherlayers of the array surface, as shown, for the particular case ofelectrodes 1. Raised layers may be placed together on opposing electrodearray sheets to form a flow path 4.

As shown in FIG. 8, flow path 4 may be formed by either aligning ormisaligning of grooves, ridges, or bumps represented by any combination,either together or different, of the current collector 6, electrodes 1,or dielectric spacer 2, when put together to form flow paths 4 from twoelectrode arrays 7. As an example, two planar electrode arrays 7 areprepared. In the first array, either or both of electrodes 1 anddielectric spacers 2 can be formed on a substrate layer as a raisedlines, bumps, or the like. The second electrode array 7 is formed in alikewise manner, by forming electrodes 1, dielectric spacers 2, andoptionally, current collectors 6 as raised lines or other. When thesetwo arrays are put together, the lines or shapes are offset in order toform biplanar other flow channels, as shown in FIG. 8. Alternatively,any of the materials of the present invention may contain grooves orform grooves in combination with any other layer material, in order toform flow channels when put together with another similar electrodearray, or with simply another sheet material, for example, a plasticfilm.

Another method to create a flow channel is to use a separate flow spacer3 between electrode array sheets. Any membrane or spacer known to beused in reverse osmosis, flow-through capacitors, batteries, fuel cells,or capacitors can be used as an electrically-insulating layer and/or asa flow spacer 3 between electrode arrays.

Geometries which allow for anode-cathode pairs of electrodes 1 orelectrode material where the majority of the facial surface does notdirectly oppose the opposite polarity electrode 1 will form theelectrode array of the present invention. One way to achieve this is forthe electrodes to be coplanar. Anodes and cathodes may be coplanar inthe same sheet of material. Alternatively, electrodes 1 which comprise,at any one time, anodes or cathodes, which may be contained in differentsheets, separated by a spacer, while at the same time having less than50% of their facial areas directly opposing each other, according to thepresent invention. For example, electrodes 1 made as arrays of lines orother shapes may be made into separate anode and cathode sheets, whichmay be placed on top of each other and separated by a spacer layer. Theonly portion of these lines that would oppose each other would be whenthe lines or shapes intersect. More than 50% of the facial area of theelectrodes would not be directly opposed to each other. In the casewhere anodes and cathodes are formed on the same sheet of material, theamount of overlap between separated sheets of materials does not matter.When electrode array sheets containing both anodes and cathodes withinthe same sheet are layered, these array sheets may be electricallyisolated by means of an extra thick spacer, for example, over 0.001inches thick, without increasing electrical resistance. The thickinsulating spacer in this case also serves as a means to containelectrolyte. However, unlike in the prior art, making this spacer thickin order to insulate one layer from the next does not increaseresistance. The resistance is governed by the space between the lines orshapes that form the electrode array. Electrodes 1 formed as lines,strips, or rectangles upon a flat nonconductive surface, with the widestcapacitive surface of the electrode 1 in the same plane as thenonconductive spacer surface 2, will form a capacitor, battery,electrochemical cell, or anode-cathode pair or grouping or electrodearray 7, according to the present invention. In this case, theelectrodes 1 are also coplanar with the current collector 6 anddielectric spacer 2. The widest capacitive surface or surfaces off theelectrodes 1 may also be offset from the plane of the spacer or spacedapart layers. For example, the capacitance or electrochemical electrodes1 may be formed as indentations, grooves, or sides of holes cut into anelectrode material.

Any of the layers represented in FIGS. 1-8, including dielectric spacers2, flow spacers 3, insulators, electrodes 1, or current collectors 6 canbe manufactured by any of the following methods: extrusion, photomasking, photolithography, lithography, screen printing, intaglioprinting, stenciling, drawing, spraying, electroplating,electrostatically sticking, electrocoating, embossing, photo engraving,ink-jet printing, laser printing, off-set printing, contact printing,thermography, digital printing, gravure printing, as well as anyoptical, digital, photographic, light sensitive, or any other maskingtechnique known to be used in the coatings, printing, circuit board,optical, or semiconductor industry.

FIG. 9 depicts an alternative design of a flow-through capacitor orflow-through electrochemical cell utilizing the electrode array 7 of thepresent invention. Electrode array 7 is shown in FIG. 9 in a spiralwoundconfiguration, but may be any geometry of layers with a flow pathalongside or through the layers. As shown in FIG. 9, flow path 4descends downward through electrode array 7, inside cartridge holder 11.A power supply 9 can supply electric power to the anode-cathode pairs ofthe electrode array 7. Pretreatment item 10 can optionally be includedin the electrochemical system of FIG. 9, as determined by one skilled inthe art. Without limitation, in one embodiment, pretreatment item 10 canbe a source of an anti-foulant chemical, acid, or polyphosphate that ismetered into the fluid feed stream when the cell is used as aflow-through capacitor, or alternatively only during theconcentration-waste generating cycles of operations. Where used as afuel cell, a fuel tank or source may be added, and a storage battery orelectrical load may be provided. Valve 13 can be controlled bymechanisms known to those skilled in the art, such as a computer, alogical controller, a conductivity sensor, a timer, or a relay. Wherethe electrode array 7 is used in a flow-through capacitor, valve 13 canbe a means of separating the waste product part of a flow-throughcapacitor cycle.

In additional alternative embodiments, the electrochemical system canfurther comprise an accumulation tank, and may be, for example, abladder tank. Cartridge holder 11 may be engineered so that thecartridge or electrode array 7 can be easily removed. An existingcartridge-cartridge holder combination common to the water filtrationindustry can be adapted for this purpose, as would be understood tothose skilled in the art. Any existing means of connecting a removeablebattery to a load while inside a device or cartridge may be duplicatedas a means of providing power to the cartridge or electrode array 7inside of the cartridge holder 11.

The electrode arrays of the invention can be prepared with the materialsdiscussed below.

Electrodes

The electrode material may be, without limitation, a fringe fieldelectrode, a carbonaceous material, a conductive polymer, ceramic, metalfilm, aluminum or tantalum with an oxide layer, metalized polymer orMYLAR®, a binder carbon mixture, a binder carbon powder mixture, apolytetrafluoroethylene (PTFE) carbon powder, PTFE carbon black, or PTFEactivated carbon mixture. One preferred embodiment is to use a carbonmaterial having a surface specific capacitance of about 5 microfaradsper square centimeter of electrode surface area, where single electrodecapacitances are measured in concentrated sulfuric acid or in 0.6 Msodium chloride (NaCl). The electrode surface area above refers to theinternal surface area of the electrode material, as measured by theB.E.T. or nitrogen absorption method.

Also useful as an electrode material of the invention are thosematerials that provide over 1 farad/cubic centimeter capacitance. Carbonis particularly advantageous, due to the fact that carbons may beselected for long life times, for example, over 1000 hours, while cyclecharging in 0.6 M NaCl. Forms of carbon that may be used include,without limitation, carbon black activated carbons, aerogels, reticlecarbons, nanotubes, high capacitance carbon blacks, alkali- andacid-activated carbons, carbon fibers, and carbons selected forresistance to oxidation.

Where it is desirable use an electrode material that includes a binder,various forms of binder may be used, including latex, polyolefins, PTFE,phenolic resin, and carbonized binders. Binders known to the art andused to bind carbon particles together in capacitors may be employed,including sintered organic binders. A particularly advantageous form ofbinder is a polyelectrolyte or polymer, either cross-linked ornoncross-linked, which forms a hydrogel in water. These include, but arenot limited to, polystyrene with ionic groups, including sulfonic acidand amine groups, strong acid groups, strong base groups, as well asweak acid or weak base, or a suitable group known to those skilled inthe art to be useful in ion exchange resins. Other binders that may beused include: cross-linked, acrylic acid; methylacrylic acid;acrylamide; acrylonitrile; melamine; urethane; acrylic, heat, orradiation curable polymers; epoxy; water absorbent polymers; andpolymers modified with crosslinks, ionic, or hydrophilic groups.Hydrophilic binders are preferred. Binders that occlude less than 50% ofthe B.E.T. measured surface area of the carbon particles are alsopreferred. The amount of cross-linking may be varied from between 0.1%and 75% in order to increase ion exchange capacity.

Additional polymers and manufacturing methods of forming a polymer layermay be used as a binder to form the carbon or other conductive materialtogether into electrodes for use in the present invention. See, Gray,Fiona M., Solid Polymer Electrolytes, VCH Publ., 1991. Amounts ofcross-linking may vary from 0% to 50% or more. Suitable carbon particleelectrode binding polymers include: polyethers, polyamides, polyacrylicacid, polyamines, polyvinyl alcohol, polyvinylcaprolactam, andvinylpyrrolidone polymers, as well as any homopolymers, copolymers,block, dendritic, cage, or star polymers, comb branched, network,random, or other polymer mixtures of the above.

U.S. Pat. No. 6,183,914 B1, issued Feb. 6, 2001, discloses apolymerbased conducting membrane. This material, as well as the priorart materials cited in this patent, may be mixed with carbon particlesto be used as a binder formulation used to manufacture electrodesaccording to the present invention. Polyelectrolytes may be usedtogether or combined with electrodes as described in PCT InternationalApplication No. US01/12641, entitled “Charge Barrier Flow-ThroughCapacitor”(WO 02/086195). These polyelectrolytes may, for example, becross-linked or intertwined together so that the electrode does notswell more than 50% in water. The percent of cross-linking needed toachieve this may be 2% or more. Polyelectrolytes may be held togetherinside a different network polymer, particularly by selecting polymersor polyelectrolytes with molecular weights above 1000. Block orcopolymers may also be used. Polyelectrolytes may be derivatized, eitherbefore or prior to incorporation into the electrode, using any ionicgroup, chemistry, or manufacturing method known to be used in ionexchange resins or permselective membranes.

For use in integrated charge barriers, the hydrogel may have ionic orion exchange groups bound to it, as known to those skilled in the art.Without limitation, ionic groups described in the charge barrierflow-through capacitor of PCT International Application No. US01/12641(WO 02/096195) may be used. These ionic groups may be fixed to a bindermaterial or may be fixed to a coating, membrane, polymer, orpolyelectrolyte either as a layer on top of the electrolyte, infiltratedthroughout the electrode, used to bind electrode material together, orfixed directly to the carbon or other electrode material itself. Theamount of cross-linking may be varied so that the ion exchange capacityof the hydrogel polyelectrolyte binder may be above 0.1 milliequivalentsper cubic centimeter, for example, above milliequivalents per cubiccentimeter, up to 4-7 or more milliequivalents per cubic centimeter.High ion exchange capacity of over 0.1 cubic centimeter is advantageousto exclude ions from the pores of the electrode due to Donnan Exclusion.Ionic groups may be selected from strong acid, strong base, weak acid,weak base, chelating, ion selective, or biologically selective groups,including the use of antibodies and enzymes fixed to the hydrogelbinder.

In other embodiments, electrodes can be prepared from a carbon materialor carbon binder mixture currently used in electrochemical cells, asknown to those skilled in the art. In addition to the already citedexamples, this can include, without limitation to: polymer-graftedcarbon preparations, such as those described inhttp://ecl.web.psi.ch/Publications/Richner A00.pdf, and reticulatedcarbon, aerogel carbon, carbon fibers, nanotube carbons, activatedcarbons, carbon-hydrogel mixtures, suspensions of carbon binder mixturesformulated for use in coating processes, graphite, or any kind ofcarbon, in addition to other metallic, ceramic, polymeric, organic, orinorganic conductive materials. Optionally, any of these above materialsmay be mixed with a binder, sintered, or combined together in othercombinations.

Some electrochemical cells may beneficially require that alternateelectrodes be of different materials. For example, electrode arrays foruse in lithium ion batteries can be of alternating groups ofintercalating graphite electrodes and oxide electrodes such as, withoutlimitation, oxides of nickel, manganese, cobalt, or mixtures thereof.Solid polymer electrolytes, or other various electrolytes used in agiven electrochemical cell technology, can be used together with theelectrode array of the present invention.

Generally, electrochemical cell technology may be directly adapted tothe present invention by using their anode and cathode materials intothe anodes and cathode materials of the electrode array and using theirelectrolyte within or between electrode arrays, such as separated by afluid-containing space or spacer to contain the electrolyte. For generaluse in energy storage devices, such as lithium ion or electrochemicalbatteries, the electrodes of the present invention may be separated by aspacer whose purpose is not for flow, but to contain electrolyte. Flowspacers within the cell, together with a cartridge holder containinginlet and outlet means, may be added for fuel cells, flow-throughcapacitors, and other flow-through electrochemical cells. In eithercase, the electrolytes, electrode materials, and spacer materials usedin any prior art electrochemical cell may be used as electrolytes,electrodes, and fluid-containing spacers with the electrode array of thepresent invention.

Dielectric Spacer

The dielectric spacer used as an insulating material between theelectrodes may be a sheet of material of less than, for example, 0.1inches, preferably under 0.02 inches, for example, 0.0001-0.020 inch.The sheet may be of MYLAR®, polymer, plastic, or a nonporous or poroussheet material known to those skilled in the art. In some embodiments,the spacer may be prepared from a material that is an electric and ionicinsulator, that is electrically insulating but an ionic conductor, is amembrane, e.g., a NAFION® membrane (NAFION is a registered trademark ofE.I. Du Pont De Nemours and Company Corporation of Wilmington, Del.), amembrane of selective permeability, or a nonwoven, woven, ceramic, orother thin sheet material.

Current Collector

An optional current collector-layer may be used comprised of metal,titanium, or graphite foil or graphite coatings on a nonconductive film,or of a metal foil or film, a metallized polymer film, or of aconductive layer, such as a layer of conductive polymer or ceramicsubstrate. Foils or films under 0.1 cm thick are preferred, for example,0.02 cm or less thick. The current collector may either be coated on orembedded within the electrode, or, may serve as a flat substrate forelectrode or spacer layers.

Optional Flow Channel

Materials useful for forming a channel for the flow of fluids in aflow-through capacitor include those materials known to the art to besuitable as flow spacer in prior art flow-through electrochemical cells,including without limitation: netting, biplanar filtration netting,thermoplastic material, insect netting, nonwoven textile spacers,protrusions or bumps, and screen-printed pairs of offset lines. Flowchannels can be of a thickness chosen by one skilled in the art. Giventhat capacitance is formed within the electrode layer, flow channels maybe as thick or as thin as desired to optimize flow properties and tooptimize pressure, for example, to reduce any potential drop inpressure. Without limitation, pressures can be optimized at below 100psi, for example, 10 psi or less.

Any of the above layers may be laminated, glued, or formed together intoan integral composite material.

Numerous embodiments besides those mentioned herein will be readilyapparent to those skilled in the art and fall within the range and scopeof the invention. All references cited in this specification areincorporated by reference in their entirety. The following examplesillustrate the invention, but are in no way intended to limit theinvention.

EXAMPLE 1

A thin sheet electrode array, under 0.1 inches thick, preferably under0.02 inches thick, with alternating electrodes such as shown in FIG. 1or 2, is placed against a flow spacer. One or more electrode arraylayers are placed together with the flow spacer in any geometry used inflow-through capacitors or electrochemical cells. The electrode arrayand flow channel layers may be held together or compressed between endplates in order to form a flow-through electrochemical cell. Inlet andoutlet means are provided exactly as in any other parallel electrodeprior art electrochemical cell. The difference in the present inventionis that electrodes in any prior art electrochemical cell geometry arereplaced by electrode arrays of the present invention. A separate layerof current collectors may be placed underneath the electrode material.

EXAMPLE 2

Carbon powder PTFE electrodes of 0.01 inch thick are laminated with agraphite current collector layer and a 0.001-inch thick, nonporous,polymer spacer on one or both sides of the electrode/current collector.Arrays of holes 0.005 inches wide, spaced 0.010-inch center to center,are cut through spacer, electrode, and current collector layers in orderto form a thin sheet electrode array. This array may be spiral wound,stacked flat against, or laminated for use with a separator used to forma flow channel and formed into an electrochemical cell or flow-throughcapacitor of any prior art geometry, where the electrode array of thepresent invention replaces the electrode used in the prior art.

EXAMPLE 3

Carbon powder PTFE electrodes of 0.01 inch thick are laminated with agraphite current collector layer and a 0.001-inch thick, nonporous,polymer spacer on one or both sides of the electrode/current collector.This is subsequently stacked or rolled into a jelly roll and heattreated or glued together in order to bind the layers together into amonolith. The monolith may be a rectangle, or cylinder, or any othershape. The monolith is subsequently skived diagonally or perpendicularlyacross the layers in order to form thin electrode sheet arrays of thepresent invention for use in electrochemical cells or flow-throughcapacitors.

EXAMPLE 4

Arrays of conductive lines 0.003 inches thick, 0.0005 inches tall, andspaced apart 0.001 inches, are printed onto polymer or MYLAR® film inorder to form an electrode array of the present invention.

EXAMPLE 5

A carbon black binder mixture is screen-printed onto an insulatingspacer to form an array of lines 0.003 inches wide, 0.0005 inches tall,and spaced apart 0.001 inches. The spacer may be a polymer, porous, ornonporous, for example, MYLAR®, or a nonwoven porous polyolefin sheetmaterial, or a thin film of any polymer. Every other line extends outfurther than the next line. These lines may be connected in parallel byplacing a conductive strip down a side, back, and/or length of thealternating anodes on one side and the cathodes on the other side.Alternating the power supply means used to apply voltage to theelectrode lines may reverse polarity.

To form a current collector, a graphite or other conductive layer may beprinted or coated directly on top of the lines, in order to form aconductive layer.

EXAMPLE 6

Layers of electrode, insulating spacer, and optional current collectorare rolled into a jelly roll or into concentric circles. By use ofbinders, heat, calendars, coating, spraying or other means, these layersare formed into a composite that is subsequently skived or sliced into0.020 inch or less sheets, by cutting diagonally or perpendicularlyacross the layers. This forms electrode array sheets. These electrodearray sheets may be further layered or laminated with a flow spacer inorder to form a flow-through capacitor. The laminated electrode arraysmay be put together with additional spacers, porous spacers, ionconductive spacers, membrane spacers, nonwoven or woven or net spacers,screen-printed, open, or any other spacer means used in facinggeometries as in any other prior art flow-through capacitor orelectrochemical cell.

Flow may be through or preferably across the electrode array and throughthe flow space between the facing electrode arrays.

EXAMPLE 7

A laminate of alternating electrodes and spacers is formed by coating,spraying, electroplating, extrusion, or calendaring methods to form alog, rectangle, or cylinder which is subsequently cut into layers lessthan 0.5 inches thick, or which is extruded into thin sheets with theparallel laminations running across the width or the length of thesheet. Sheets may be less than 0.5 inches thick, for example, less than0.02 inches thick. Electrodes in this sheet may be thinly divided byinsulating spacer lines, less than 0.02 inches apart. Alternatingelectrodes or current collectors may be masked or insulated at the ends,so that a perpendicular connecting lead may connect alternate electrodeson each end to form anode/cathode pairs, as illustrated in FIG. 1.

EXAMPLE 8

A thin conductive film of graphite or polymer-backed graphite is paintedwith a photo resist masking chemical and illuminated through a patternto expose a series of lines 0.05 cm or less wide and 0.05 cm or lessapart. Upon washing, a pattern of grooves is revealed exposing theunderlying current collector material. A carbon black material of over500 BET is mixed with a 5% or more cross-linked, strong polyelectrolyteor hydrogel binder containing strong acid or strong base groups, or,alternatively, is mixed with any other binder to form a slurry. Thisslurry is wiped, sprayed, or coated onto the current collector/photoresist layer. Any excess is wiped off, revealing an alternating patternof electrode and insulating material lines. This carbon binder mixturemay be cross-linked, dried, or solidified by temperature, or by light,catalysts, time, or other methods. Two of these identical sheets may besandwiched together with a flow spacer and manufactured to form aflow-through capacitor according to any prior art flow through capacitorgeometry, such as those described in Andelinan U.S. Pat. Nos. 5,192,432,issued Mar. 9, 1993; 5,196,115, issued Mar. 23, 1993; 5,200,068, issuedApr. 6, 1993; 5,360,540, Nov. 1, 1994; 5,415,768, issued May 16, 1995;5,547,581, issued Aug. 20, 1996; 5,620,597, issued Apr. 15, 1997;5,748,437, issued May 5, 1998; 5,779,891, issued Jul. 14, 1998; or inOtowa U.S. Pat. No. 5,538,611, issued Jul. 23, 1996; or in Andelman PCTInternational Application No. US01/12641, “Charge Barrier Flow-ThroughCapacitor”(WO 02/086195). Alternatively, all layers may bescreen-printed. Electrode or spacer layers may be made as protrudingridges in order to form flow channels when two electrode arrays areplaced together in an opposing manner, with the sets of lines offset atan angle from each other.

EXAMPLE 9

The electrode array of the present invention may require the manufactureof patterned thin films of materials in juxtaposition to each other,layered together, or on top of each other. A particularly useful methodto do this is to use electrostatic or other self assembly methods, suchas those described in U.S. Pat. Nos. 6,316,084, issued Nov. 13, 2001,and U.S. Pat. No. 6,291,266, issued Sep. 18, 2001, and Spillman Jr., etal. U.S. Patent Application Publication No. 20020037383A1, publishedMar. 28, 2002, each of which is hereby incorporated by reference. Thesemethods can be used to manufacture the electrodes, spacers, and currentcollectors of the present invention. Electrostatic powder coatingtechnology can also be used to form the electrode, current collector,insulating spacer, and flow spacer layers. Especially where electrodesare dots or shapes other than lines, and need to be connected in groupsof anodes and cathodes, technology such as described in U.S. Pat. No.5,070,036, issued Dec. 3, 1991, and U.S. Pat. No. 4,977,440, issued Dec.11, 1990, can be used to form interconnecting groups of currentcollectors.

1. An electrode array for use in an electrochemical cell, said arraycomprising: at least one pair of oppositely-charged electrodescomprising: a) an anode having a first anode face and a second anodeface, said first anode face being broader than said second anode face;and b) a cathode having a first cathode face and a second cathode face,said first cathode face being broader than said second cathode face,wherein said first anode face is not directly opposed to said firstcathode face in said array; and c) a dielectric material between saidsecond anode face and said second cathode face.
 2. A sheet materialcontaining the electrode array of claim
 1. 3. An electrochemical cellconsisting of the sheet material of claim
 2. 4. The sheet material ofclaim 3, wherein said sheet material is wound in a spiral.
 5. Theelectrode array of claim 1, wherein said electrode array furthercomprises a planar substrate, and said electrodes are coplanar on saidsubstrate.
 6. The electrode array of claim 2, where said electrodes ofsaid pair of electrodes are made from a carbon material.
 7. Theelectrode array of claim 1, wherein said electrode array has a seriesresistance of less than 50 ohms/cm² of electrode array facing area, andan electrical leakage resistance of more than 30 ohms/cm² of electrodearray facing area.
 8. The electrode array of claim 1, wherein the firstanode face is separated from the first cathode face by a distance ofless than 3 millimeters.
 9. The electrode array of claim 1, wherein thesecond anode face is separated from the second cathode face by adistance of more than 0.002 centimeters.
 10. The electrode array ofclaim 1, wherein each of said electrodes in said electrode pair has aconcentric spiral shape.
 11. The electrode array of claim 1, whereineach of said electrodes has a surface area of greater than 10 m²/gramB.E.T.
 12. A flow-through capacitor comprising the electrode array ofclaim
 1. 13. The flow-through capacitor of claim 12, further comprisinga fluid flow path for the passage of a fluid across the surface of saidarray.
 14. A flow-through capacitor comprising the electrode array ofclaim 5 and a flow path for the passage of a fluid across the firstanode face and across the first cathode face in said array.
 15. Theflow-through capacitor of claim 14, wherein said flow path comprises aporous, nonelectrically-insulating material.
 16. A flow-throughcapacitor comprising: a) at least two electrode arrays of claim 5; andb) a flow path for the passage of a fluid across the first anode faceand the first cathode face of the electrodes in said array, said flowpath having a thickness of at least 20 micrometers in thickness.
 17. Amethod of lowering the series resistance of an electrochemical cell,comprising the steps of: a) providing an electrode array, said arraycomprising a planar substrate and at least one pair of electrodes onsaid planar substrate comprising an anode and a cathode, wherein saidanode has a first anode face and a second anode surface, said firstanode face being broader than said second anode face, and wherein saidcathode has a first cathode face and a second cathode face said firstcathode face being broader than said second cathode face and whereinsaid first anode face is not directly opposed to said first cathodeface; and b) inserting said electrode array into said electrochemicalcell.
 18. The method of claim 17, wherein said electrochemical cell is aflow-through capacitor.
 19. The method of claim 17, wherein saidelectrochemical cell is a lithium battery.